| Using quantum mechanical superposition and interference principles,we can design a quantum computer that is more powerful than traditional computers,but there are two major difficulties in building quantum computers:one is decoherence,quantum entanglement occurs when the quantum state interacts with the external environment under the influence of environmental noise,resulting in the coherent superposition of the quantum state disappearing with the passage of time;the second is inaccuracy,the state of a quantum superposition depends on certain continuous parameters,and all quantum gates are potentially analog in that there will be some amount of inaccuracy in any physical implementation,that is,the output quantum state will not be precisely the desired state.It is in this case that quantum error correction codes have emerged,which can be used to effectively overcome the effects of decoherence and inaccuracy in the storage,transmission and computation of quantum information.The process of quantum error correction is mainly composed of three parts: quantum state preparation,syndrome measurement and error-correction.The role of syndrome measurement is to detect the location of the error and determine the type of error.First of all,the basic requirement for this process is fault tolerance.In the measurement process,it is necessary to ensure that an error does not propagate into a multi-qubits error that cannot be corrected by the quantum error correction code.Secondly,it is efficient,and the less resources are consumed,the easier it is to make quantum computers available for practical use.In this paper,we mainly study the existing methods for the fault-tolerant syndrome measurement of quantum error correcting codes.On this basis,we propose a new scheme to reduce the time required and the ancilla qubits overhead for measurement,and design the corresponding measurement circuit diagram,as follows:Firstly,the basic theory of quantum error correction codes involved in this paper is introduced.Focus on the construction,coding and error correction process of quantum stabilizer codes,and analyze the principle of error propagation in the measurement process,and deeply study the current methods of fault-tolerant syndrome measurement of several quantum error correction codes,and introduce the basic principles in detail.Second,puts forward an efficient dynamic slot allocation scheme based on the “flag” syndrome measurement method.For the quantum CSS code,this scheme can measure all the same type of stabilizers simultaneously,use the CSS codes with the same and different stabilizer weights as examples in this paper to demonstrate the implementation process of the scheme,design the corresponding syndrome measurement circuit diagrams,and give detailed analysis of the error syndromes of the circuits when a one-qubit error is occurred.While ensuring the fault tolerance of the measurement method,the time cost is reduced and the parallelism of the circuits is increased.The general automation process design of this scheme is given.The computer program simulation results show that the number of time slots required for the stabilizers syndrome measurement in this scheme is 1 m of the original scheme.Third,a low-consumption measure scheme of Shared token bit symptom is proposed,which enables multiple stabilizers to share one token quantum bit when measuring symptoms in quantum CSS code.Taking the concrete CSS codes as examples,the implementation process of this scheme is illustrated,and the corresponding syndrome measurement circuit diagram design is given,and all possible error syndromes in the circuits are explained in detail.On the premise of fault tolerance,the number of ancilla qubits is reduced.The general automation process design of the scheme is given.Compared with the similar schemes,the number of ancilla qubits required for the stabilizer syndrome measurement is greatly reduced.Finally,summarize the full text and look forward to the next research direction. |
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